Periodontal indexes of two types of 3 x 3 retainers: 0.032-in SS V-loop versus 0.0215-in SS coaxial - a randomized crossover trial

ABSTRACT Objective: This randomized crossover trial evaluated periodontal indexes of two types of 3 x 3 retainers (a modified 0.032-in SS V-loop retainer and a conventional 0.0215-in SS coaxial wire retainer) after bonded for six months. Also, bonded failure rate, and a questionnaire about comfort, ease of cleaning and overall preference were recorded. Material and Methods: 15 patients were enrolled in this study who used both retainers for six months each, having a 15-day wash-out interval between each bonded retainer usage. The following periodontal index were recorded: Plaque Index (PI), Calculus Index (CI) and Gingival Index (GI). Patients answered a questionnaire to assess comfort, ease of cleaning and overall retainer-type preference. Rate of bonding failure was also evaluated. Results: V-Loop retainer showed higher PI (P<0.05) as compared to conventional 0.0215-in coaxial wire retainer. However, CI and GI presented no statistically significant differences between both types of retainers. The conventional 0.0215-in coaxial wire retainer was chosen as the most comfortable (p<0.05), although no statistically significant differences were found for all other questionnaire answers. Bonding failure events were more observed in the 3x3 V-Loop retainer (p<0.002), as compared to the conventional 0.0215-in coaxial retainer. Conclusion: V-Loop retainer showed higher PI (p<0.05), higher bonding failure rate and less comfortable, as compared to conventional 0.0215-in coaxial wire.


INTRODUCTION
2][3][4][5][6] Vacuum-formed or Hawley appliances are the most common options for the upper arch, and bonded wires contoured from canine to canine are the most recommended choices for the lower arch.
Thus, such retainers should be comfortable and easy to be cleaned, helping periodontal health with time.In 2015, a 3x3 V-loop retainer was suggested, presenting a design with V-formed curves perpendicular to the tooth axis to be easy to clean, as well as overall stability properties of retainers. 8,9wever, no study tested such characteristic on periodontal condition with time.
Dental Press J Orthod.2023;28(6):e2323175 Thus, the aim of this study was to evaluate periodontal indexes of two types of 3 x 3 retainers (a modified 0.032-in SS V-loop retainer and a conventional 0.0215-in SS coaxial wire retainer).
e sample calculation was performed considering the primary variable PI, using G*Power 3.1 software.For repeated measurement tests between factors, with sample effect equal to 1, beta value 0.95 and alfa 0.5, considering two groups, two measurements, the resulting sample size was 14.However, based on previous studies, 19 patients were recruited, considering a drop out of 20%. 17,18clusion criteria were as follows: good periodontal health condition, no-smoking habit, no systemic disease, well-aligned lower anterior teeth or maximum of 2-mm irregularity, righthanded and aged 18 to 30 years-old.Exclusion criteria were as follows: undergoing orthodontic treatment at the time or presenting any coordination disability.This experimental protocol was based on previous studies. 17,18The patients were given randomly generated envelopes.This was a crossover study, presenting the following phases in the experimental design (Fig 1 ): A. Baseline -All individuals (n=19) underwent scaling, and dental prophylaxis was performed 15 days prior to the use of retainers.On day zero, periodontal parameters were normal.

This randomized crossover trial was approved by the Ethics
B. After retainers confection, 9 patients used the 0.0215" coaxial retainers and 8 used the V-loop retainer for six months.
Periodontal parameters were recorded at the end.
C. Washout -With drop out equivalent to 4 patients, this phase was reached with 15 patients.All retainers were removed, along with the removal of residual resin, in addition to polishing, and a 15-day interval was used for normalization of the parameters.D. A new retainer was bonded, as follows: Patientes who had used the V-loop type started using the coaxial retainer, and vice versa, for another six months.Periodontal parameters were recorded at the end.
All patients received instructions to perform oral hygiene three times a day, and received a hygiene kit comprising a toothbrush Odontológicos -EirelI, Pinhais/PR, Brazil).Two hygiene kits were given to the patients, one for each retainer test interval.
They were instructed to use the Bass method 19 , which involves holding the toothbrush at an angle so that the bristles point at the gum line and making short back-and-forth strokes, followed by sweeping the brush from under the gum toward the edge of the tooth.
All the periodontal evaluations were performed by the same operator.The calibration of the evaluator was submitted to the Kappa agreement test for 20% of the sample, and the result obtained was 0.91 (p<0.05).
At the end of the twelve months, the patients answered a questionnaire to evaluate both retainers regarding comfort, easiness to hygiene, the necessity of a floss guide and their overall preferred retainer type.Dental plaque index (PI), 20 dental calculus index (CI), 21 and gingival index (GI) 22 were recorded.PI evaluation followed the simplified Silness and Löe method. 20Each tooth was divided into three surfaces (mesiolingual, distolingual and lingual), and then separated by the lower, middle, and upper thirds.
The plaque was evidenced with 1% toluidine blue dissolved in distilled water.Scores from 0 to 3 were recorded: 0 = absence of plaque; 1 = presence of plaque on at least 1/3 of the tooth surface, 2 = presence of plaque in 2/3 of the tooth surface, and 3 = presence of plaque in 3/3 of the tooth surface.
Then, the median for each surface was calculated (Fig 3 ).Table 1 shows the frequency and percentage of PI, per dental surface for both groups.PI was slightly higher (p<0.01)for V-loop retainers in all evaluated surfaces (mesiolingual = 57.8%,distolingual = 56.7% and lingual = 57.8%)(Figs 4, 5 and 6).Tables 2 and 3 show the frequency and percentage for dental CI and GI.There were no statistically significant differences between the retainers.Questionnaire results are presented in Table 4, where 87.7% of the patients opted for coaxial retainers regarding comfort (p< 0.05).On the other hand, 60% reported that the V-loop retainers were better to be cleaned, but without statistical significance.Regarding the need for the floss threader, no clinically difference were registered.Considering overall retainer preference, 66.7% choose coaxial group and 33.3% liked the V-loop retainers, however with no statistical difference.
When evaluating hygiene efficiency on the right and left sides, the PI was more evident on the right side (p<0.001).However, GI presented a statistically significant difference only for the V-loop retainers in the lingual surface (p<0.016).The CI showed no difference between both sides.

DISCUSSION
23,[27][28][29] The results indicate the rejection of the null hypothesis and show a statistically significant difference between the retainers regarding the PI, which was slightly higher for the V-loop retainers, for all evaluated surfaces (Table 1).However, GI and CI did not differ between groups, presenting only a slightly greater accumulation of plaque and a slight gingival alteration in the V-loop retainers (Tables 2 and 3).For this reason, the retainers can be considered clinically similar in terms of the periodontal aspects.
A previous study that considered the retainers bonded to all the teeth concluded that these retainers show a greater accumulation of plaque and calculus than those bonded only to the canines. 10Although bonding on all teeth implies greater plaque and calculus accumulation, another study conducted a systematic review to evaluate the stability after orthodontic Dental Press J Orthod.2023;28(6):e2323175 treatment comparing the retainers bonded to all the teeth and those bonded only to the canines.The authors concluded that stability was higher for the retainers in which all lower anterior teeth were bonded. 23zatta et al. 14 conducted a systematic review with the intention of evaluating the periodontal parameters of fixed retainers that do not prevent the access of dental floss, compared to those that do.Clinical trials and cross-sectional studies that compare the two types of retainers were included.Four studies met the inclusion criteria, and all presented risk of moderate bias.Two of these studies found a statistically significant difference in gingival indexes, while the other two did not report any difference.They concluded that there is no evidence to either support or refute the association between the type of retainer and gingival health, but rather a higher flossing frequency may be a determining factor for periodontal health during the use of these retainers.
On the other hand, Lukianchuki et al 24 compared the multistranded wire retainers and the modified wave-type retainers, and observed that the straight wire retainers presented better results in relation to the modified ones, when it comes to periodontal parameters, comfort, and preference.Therefore, they considered that the type of retainer interferes with these parameters.
Dental Press J Orthod.2023;28(6):e2323175 To ensure stability after orthodontic treatment, the orthodontist should bond the retainer on all lingual surfaces of the six lower anterior teeth.However, this condition leads to a greater accumulation of plaque and calculus in those teeth.It is important to highlight that lack of hygiene and flossing is one of the main factors for the change in periodontal health.
In the present study, patient variable was eliminated, since the patients used both types of retainers.V-loop retainers were considered by the patients to be the most appropriate for hygiene due to its design, with no impediment to flossing.However, it seems that the greater accumulation of plaque occurred due to the greater contact area between wire and lingual surface of the lower anterior teeth and the loops of the retainers, creating a mechanical barrier for the brush bristles.
In the present study, the patients preferred the comfort of the coaxial retainers and the ease of performing hygiene with slight advantage for V-loop retainers, but in general the coaxial retainers were preferred, but without significant differences (Table 4).
Patients reported that the V-loop retainers bothered their tongue, almost like having a "spur".While the coaxial ones were easier to adapt to, for not having an overjet and allowing more space for the tongue.However, V-loop retainers could be used The sample in this study included right-handed individuals who brushed better on the left side.This curious fact was confirmed by the PI altered for the right side, corroborating those studies seen in the literature. 30,31It is worth mentioning that the CI and GI (except for the V-loop retainers on the lingual surface) did not show any statistical difference regarding hygiene, when comparing the right and left quadrants of the lower anterior teeth.Although it was not the main target of the present study, it seems interesting to warn right-handed patients regarding the care when brushing their right lower teeth, and theoretically the inverse for left-handed patients. 31other secondary outcome was regarding the higher prevalence of bonding failure in V-loop retainers, compared to coaxial retainers, corroborating previous studies. 32V-loop retainer has an extension towards the lingual, to some extent it creates a plateau that receives more vertical forces when chewing.It should also be checked for possible partial debonding and the consequences this might have to the periodontium.
Furthermore, it is possible to say that bonding failure may compromise stability, as the patient may not promptly identify such failure, and teeth may move.Besides that, periodic revision is indicated for all types of the retainers, to prevent complications 13,32 (Table 5).As a limitation of this study, one may consider that six months of observation may not be sufficient to understand the impact of retainers in the periodontium.However, in a classical study, Löe 33 investigated the evolution of gingivitis formation and how the periodontium behaves with time.A formation of gross accumulations of soft debris and subsequent marginal gingivitis were observed.The time taken to develop gingivitis ranged from 10 to 21 days.Therefore, we considered this study to establish the minimum exposure time of retainers in the oral environment.This experimental protocol was based on previous studies 17,18 demonstrating that six months is enough time to check for such periodontal indexes evaluation comparing retainers type.
The results of the present study indicate that the coaxial retainers behaved slightly better on the periodontal condition in short time.However, as those differences were clinically small, V-loop retainers may be a viable alternative.V-loop retainer could be indicated for those patients who choose the ease of flossing to the detriment of comfort (or were treated for open bite), while the coaxial ones can be indicated for those patients who value comfort even if it makes flossing a little more difficult.

Sapata
DM, Silva CO, Pascotto RC, Poleti TMFF, Arai MSI, Ramos AL -Periodontal indexes of two types of 3 x 3 retainers: 0.032-in SS V-loop versus 0.0215-in SS coaxial: randomized crossover trial Dental Press J Orthod.2023;28(6):e2323175The V-loop retainer was made by a single operator on the plaster models.The V-loop retainer was made with a 0.6-mm stainless steel orthodontic wire (Morelli, Sorocaba, Brazil) respecting the model with "v" bends moving away from the proximal surface of the tooth by 2mm and forming a curve perpendicular to the long axis of the tooth (Fig2).The conventional 0.0215-in SS coaxial retainer (Orthometric, Marília/SP, Brazil) was contoured for the six lower anterior teeth.All retainers were bonded by using the same resin composite (Resin Z100TM 4g -3M, Joinville/SC, Brazil), performed by a single operator.A OneGloss PS tip drill (Shofu, São Paulo/SP, Brazil) was used for polishing.

Figure 3 :
Figure 3: Diagram used for periodontal measurements recording.

Sapata DM, 20 Dental
Silva CO, Pascotto RC, Poleti TMFF, Arai MSI, Ramos AL -Periodontal indexes of two types of 3 x 3 retainers: 0.032-in SS V-loop versus 0.0215-in SS coaxial: randomized crossover trial Research Committee of the State University of Maringá (CAEE: 12854719.1.0000.0104).The patients signed a free and informed consent form, in accordance with the Guidelines and Regulatory Standards of the National Health Council (Resolution No. 196/96), following the CONSORT 2010 statement.

Table 1 :
Frequency and Plaque Index scores for V-loop and coaxial retainers.

Table 2 :
Frequency and Calculus Index scores for V-loop and coaxial retainers.

Table 3 :
Frequency and Gingival Index scores for V-loop and coaxial retainers.

Table 4 :
Questionnaire results for the two types of retainers after twelve months.

Table 5 :
Bonding failure rate for each type of retainer.